Locator

ABSTRACT

MY DISCLOSURE IS OF A DEVICE FOR PROJECTING A BEAM OF HIGH FREQUENCY, STACCATOLIKE, ACOUSTIC PULSES WHICH, WHEN DIRECTED TOWARD A DISTANT OBJECT CAPABLE OF REFLECTING AN ECHO, WILL ENABLE THE USER TO DETERMINE THE DISTANCE AND CHARACTER OF THE OBJECT BY INTERPRETING THE QUALITY OF THE ECHO. THE DEVICE INCLUDES A HOUSING IN WHICH IS CONTAINED A LOUDSPEAKER, AN ELECTRICAL PULSE-GENERATING CIRCUIT CONNECTED TO THE SPEAKER AND A HORN ASSOCIATED WITH THE SPEAKER FOR CONFINING THE ACOUSTIC PULSE IN A DIRECTIONAL BEAM.

United States Patent [72] Inventors Stephen L. Moshier;

William B. Van Lennep; Edmund G. Perry,

Cambridge, Mass. [21] AppLNo. 731,039 [22] Filed May22, 1968 [45]Patented Jan.26, 1971 [73] Assignee Listening Incorporated Arlington,Mass.

a corporation of Massachusetts [54] ACOUSTIC LOCATOR 1 Claim, 2 DrawingFigs.

52 U.S.Cl 179 1,

340 1 51 lnt.Cl G0ls9/46 so FieldofSearch 179 1,

1 MEG; 340/ l [5 6] References Cited UNITED STATES PATENTS 3,337,8398/1967 Nelkin 340/1 3,412,207 1 1/1968 Sugawara l79/l 3,454,922 7/1969Dory 340/l Primary ExaminerKathleen Hi Claffy Assistant Examiner-DouglasW. Olms Attorney-Kenway, Jenney and Hildreth ABSTRACT: My disclosure isof a device for projecting a beam of high frequency, staccatolike,acoustic pulses which, when directed toward a distant object capable ofreflecting an echo, will enable the user to determine the distance andcharacter of the object by interpreting the quality of the echo. Thedevice includes a housing in which is contained a loudspeaker, anelectrical pulse-generating circuit connected to the speaker and a hornassociated with the speaker for confining the acoustic pulse in adirectional beam.

PATENTEU MG Ian;

INVENTORS' NEP I FIG. 2

TTORNEYS' ACOUSTIC LOCATOR SUMMARY OF THE INVENTION My inventionincludes a speaker or similar device capable of emitting an acousticpulse of relatively high frequency and of short duration. The speaker iscombined with a horn which serves to confine the acoustic pulse into abeam so that the beam may be directed towards a distant echo-producingobject thus enabling the user to serve the presence, distance andcharacter of the distant object by means of its echo. Electrical circuitmeans are provided to energize the speaker repeatedly and cause it toemit the acoustic pulses. Means are further provided for varying therepetition rate of the outgoing pulses.

My invention may be used in numerous environments among which are as anavigational aid for mariners, blind persons, or in testing the acousticqualities of a building or other structure. The device may also beuseful in an alarm system (security and tire protection), mapping andmotion detection in general. It is not necessarily restricted to use inan atmospheric environment but could be used in any medium, such aswater, capable of conducting acoustic pulses. When used in water,however, it obviously must be of waterproof construction.

In testing my invention with a number of people, I found that after arelatively short period of practice each of the blindfolded subjects wasable to discriminate between the reflected echoes of wooden buildings,automobiles, a fence and an apartment house. The subjects were able tonavigate along a sidewalk by reference to the reverberant sounds ofbuildings and the curb as well as sensing people approaching from adistance of twenty to thirty feet.

Tests were also conducted on a boat and I found that once the testedsubject became familiar with the different reflective sounds of objects,such as buoys, channel markers and boats, he was able to give directionsto the operator of the boat to guide him through a channel and under abridge. Shore lines, islands and anchored boats were also distinguished.Tests producing such satisfactory results were conducted withblindfolded test subjects as well as in actual fog and reducedvisibility.

My invention will now be described in greater detail with reference tothe accompanying drawings wherein:

FIG. 1 is a broken away side elevation of my device; and

FIG. 2 is a schematic of the electrical pulse generating circuit.

As illustrated in FIG. 1, my invention includes a housing having an openforward end. A speaker 12 is mounted within this opening of the housing10. A bracket 14 is supported within the frame 10 by conventional meansand serves to support other elements of the device such as a battery 16and an electrical circuit 18. A born 19 is provided at the forward openend of the housing 10 to confine the sound emanating from the speaker 12to form an acoustic beam. I have found that an acoustic beam having amaximum arc width of approximately 60enables the beam to cover arelatively wide area and yet retain its directionality. For example, ahorn that is 3 inches long and enlarges from a 3 inch diameter at itsrearward end to a 6 inch diameter at its forward end produces a beamhaving a desirable arc width. The horn 19 may be removably mounted tothe housing 10 to enable substitution of a horn of a ditferentconfiguration which may project a more narrow acoustical beam. Confmingthe beam to a more narrow width would cause the device to have moresensitive directional characteristics in that the beam would have to bemore accurately directed to the acoustic target in order to produce thestrongest echo.

The speaker 12 is connected to the output of the electrical circuit 18,which may be of conventional design and is intended to repeatedlygenerate an electrical pulse of a relatively short duration so that thespeaker 12 may emit a series of high frequency staccatolike clicks. Thecircuit 18 incorporates means to vary the rate at which the pulses arerepeated. In use the pulse repetition rate is intended to be adjusted sothat when the horn is directed toward a distant object or acoustictarget, the echo from a pulse will return to the users ear before thefollowing acoustic pulse is emitted by the speaker. It has been founddesirable to vary the pulse repetition rate so that the echo returnsapproximately midway between outgoing pulses. The pulse repetition raterequired to enable the echo to return midway between outgoing pulsesprovides an indication of the distance between the device and theacoustic target. When the target is close, the echo will be quicklyreturned and the pulse repetition rate must be increased. When thetarget is distant, the greater echo return time will require a slowerpulse repetition rate.

The electrical pulse-generating circuit is schematically illustrated inFIG. 2 and includes an on-off switch 20 that may be closed to causecurrent to flow from the battery 16. When the switch 20 is closed, thecapacitor C2 is charged. A relaxation oscillator circuit, shown at 24,acts as a triggering circuit for silicon control rectifier 22. When therectifier 22 is enabled, the charge stored in the capacitor C2 passesthrough the rectitier 22 and the coil of speaker l2 causing the speakerto emit a click. The relaxation oscillator circuit 24 is of conventionaland well-known design. A full explanation of its operation may be had byreference to page I93 of the sixth edition of the Transistor Manualedited and published by General Electric Company, Syracuse, N.Y.

A preferred embodiment of my invention generates an electric pulsehaving a l0-90 percent rise time lying in the range of 208O microsecondsand a relatively long delay time constant in excess of l millisecond.The pulses are generated at a rate that is determined by the setting ofa control knob 28 (see FIG. 1) which in turn determines the value of R2in FIG. 2. A desirable range for the pulse repetition rate is between0.2 and 200 pulses per second. The pulses may have a peak amplitude of15 volts into an 8 ohm speaker generating approximately 28 watts ofpower. This would be typical of a practical unit. Some representativevalues for the schematic diagram of FIG. 2 are as follows:

Cl O.5 microfarads;

C2 --2.2 microfarads; and V 9-27 volts.

The unijunction transistor 26 may be of the type 2N2646, and thesilicon-controlled rectifier may be of the type MCR2305-c0.

The combination of the speaker 12 and horn 18 should preferably have alow frequency cutoff value between 1 and 5 kilocycles in order toproduce the desired high frequency staccato clicks. The circuit 18provides an electrical exciting signal to the speaker 12 which causesthe speaker-horn combination to emit an acoustic pulse at its naturalresonant frequency. I have found that any acoustic pulse duration of 0.2milliseconds is about optimum for most of the contemplated uses andhence a resonant frequency of about 2.5 kilocycles is appropriate.

As mentioned above, my device has practical application as a safetydevice for boat owners during periods of reduced visibility as well asfor use for the blind as an oriented device in walking. I have foundthat with little practice the user will become accustomed to thedifferent echoes produced by various targets. Tests by yachtsmen havedemonstrated that the device's useful range exceeds half a mile in airover open water. With little difficulty one may also be able to sensethe relative distance of one acoustic target from another. My device maybe of simple, lightweight construction and preferably should feel andhandle like a flashlight.

The foregoing is intended merely as an illustrative example of myinvention and should not be construed as limiting its scope except asset forth in the appended claims. Other embodiments may be constructedwithout departing from the spirit of my invention. For example, amechanically operable device could be substituted for the electricalpulse generator.

We claim: 1. Acoustic echo object'locating apparatus, said apparatuscomprising:

a loudspeaker having means for confining acoustic energy emittedtherefrom to a relatively narrow beam, said loud speaker with saidconfining means having a natural resonant frequency in the order of 2.5kilocycles;

means including an electronic oscillator for energizing said loudspeakerwith repetitive pulses; each having a duration generally correspondingto said resonant frequency, thereby to cause said speaker to emit asuccession of audible acoustic pulses, said oscillator including meansfor adjusting the pulse repetition rate to permit successive pulses tobe timed so that echoes of said pulses returned from an object in thebeam path occur midway between transmitted pulses thereby presenting arelatively easily perceived condition to an operator of the apparatus;and housing means for holding said loudspeaker, said energizing means,and a battery for powering said energizing means in a unitaryconfiguration adapted to be hand held; whereby objects may be located byaiming the apparatus to direct said. beam against an object and byadjusting the pulse repetition rate until the operator perceives thatechoes from the object occur midway between trans mitted pulses, thepulse rate so determined being indicative of the distance to the objectwith the aiming of the apparatus being indicative of the direction ofthe object from the operator.

